(Source: China Food News)
Translated from: China Food News
Functional bread "has become a hot topic in the baking industry in recent years. Adding plant flour to flour can not only supplement dietary fiber and achieve low GI properties, but also add a touch of" antioxidant "aura. Coffee powder was naturally included in this list due to its inherent "healthy" persona.
Coffee bread is no longer a novelty, from coffee croissants to coffee toast, with dark cut surfaces and a smoky flavor, it has almost become a standard feature of "high-end". But when coffee, which has antioxidant properties, is added to the dough and fermented and baked, how much of this' power 'is left? Is it marketing rhetoric or does it really have scientific basis? You can look for answers from two dimensions: the mechanism of activity and baking tests.
How does caffeine resist oxidation? Three types of active substances work
To determine whether coffee powder can enhance the antioxidant capacity of bread, it is first necessary to clarify who the "main antioxidant force" in coffee is and whether they can withstand the entire process of bread making.
The antioxidant capacity of coffee is not solely attributed to a single component, but rather the result of the synergistic effect of three types of bioactive substances.
The first type is phenolic acid compounds, led by chlorogenic acid. It is the highest content of phenolic compounds in coffee, accounting for 4% to 14.4% in green beans. The advantage of chlorogenic acid lies in its ability to neutralize free radicals, inhibit inflammatory factors, and regulate antioxidant enzyme activity through multiple pathways. Although high-temperature roasting can partially degrade it, even coffee beans that are medium to deep roasted still retain considerable phenolic acid activity. When it is ground and added to the dough, this "residual" chlorogenic acid has a chance to migrate into the bread substrate.
The second type is alkaloids – caffeine and cucurbitacin. Caffeine is the most familiar coffee ingredient to people. In addition to refreshing, it itself has certain antioxidant and neuroprotective effects. Fenugreek accounts for 1% -3% of the weight of coffee dried tofu. During roasting, although part of demethylation will be converted to nicotinic acid, its anti-inflammatory and antioxidant activities still exist. More importantly, these alkaloids have good thermal stability and will not easily be completely destroyed during the subsequent baking process.
The third category is baked goods – terpenoids and melanoids. Diterpenoid substances such as caffeic acid and caffeic acid, as well as melanoids produced by the Maillard reaction, also have biological effects of antioxidant and anti-inflammatory. Especially melanin, it has been proven to reduce pro-inflammatory cytokine levels by inhibiting inflammatory pathways such as NF – κ B. And these substances themselves are the "factory configuration" of coffee powder.
From a mechanistic perspective, coffee powder does indeed contain a complete set of "antioxidant toolboxes", but in the complex system of bread, can this toolbox still be opened?
Two levels in dough – fermentation and baking
Many bakers are concerned whether yeast fermentation will "eat up" polyphenols? Will high-temperature baking destroy it?
According to current research findings, the answer may be more optimistic than imagined.
On the one hand, chlorogenic acid exhibits good thermal stability in food. Researchers have used roasted coffee bean water extract instead of water in bread formula to compare the polyphenol composition of dough and baked bread. The results showed that roasting did not significantly reduce the phenolic content and DPPH/ABTS clearance rate of bread, and the antioxidant capacity was basically the same before and after roasting.
On the other hand, during dough fermentation, yeast does consume some small molecule nutrients, but most polyphenolic substances are firmly adsorbed and distributed in the matrix structure interwoven with gluten and starch, and the actual loss is very limited.
A control experiment using high gluten wheat flour as the base and adding 1% -4% gradient coffee powder to make bread showed that as the amount of coffee powder gradually increased, the total phenolic content of the bread product could be increased by up to 29.6%, the DPPH clearance rate increased by 133%, and the ABTS clearance rate increased by 60%. When the amount of coffee powder added is 2%, the sensory acceptance of the finished bread reaches its peak.
In a similar study conducted by a Malaysian university, green coffee powder (GCB) with gradients of 3%, 5%, and 7% was used to replace some wheat flour to make bread. After baking at 220 degrees Celsius for 30 minutes, the total phenolic content of the bread in the 3% addition group increased significantly, and the IC50 value for DPPH radical scavenging increased from 11.25 mg/mL to 3.28 mg/mL (the lower the value, the stronger the free radical scavenging ability). At the same time, the chelating ability of iron ions in the sample also significantly increased. This result indicates that even after undergoing the entire bread making process, the activity retention and synergistic effect of coffee polyphenols can still significantly increase the basic antioxidant level of bread.
Adding coffee powder must be done in moderation
The stronger the antioxidant capacity, the better the taste of the finished bread. It's like chili peppers can enhance flavor, but adding too much can make it difficult to swallow.
So, how much coffee powder can be added to achieve significant antioxidant effects without affecting the flavor? The answer is 2%. At this addition level, the surface of the bread appears light yellow brown, with the best glossiness and the highest flavor rating. Continuing to increase the addition amount, although the antioxidant effect can be further improved, will directly sacrifice the fluffiness, texture performance, and consumer acceptance of the bread. Chlorogenic acid itself is acidic, and excessive addition of coffee powder can disrupt the continuity of the gluten network. The specific volume of bread will significantly decrease, and the core will appear green. Bitter and "aged" odors will also be highlighted.
In addition, using coffee liquid instead of formula water, although the operation is simple, the high-temperature extraction itself has already caused some polyphenol loss; Mixing ultrafine coffee powder directly into dry ingredients results in shorter heat exposure time and better retention of phenols compared to liquid methods.
Here are 3 suggestions for bakers:
Firstly, it is recommended to use ultra-fine powder ground from medium and light roasted coffee beans, and add it to the dough at a ratio of 1.5% to 2% of the total flour weight. This can ensure a reasonable increase in antioxidant activity without damaging the basic taste and texture of the bread.
The second option is to use a conventional temperature range of 200-220 degrees Celsius to complete the aging process, without the need to deliberately pursue a dark brown skin color. Overroasting can lead to carbonization of polyphenolic substances in coffee, and even melanoidins, which originally enhance flavor, can deteriorate, ultimately damaging the overall flavor.
Thirdly, coffee powder is used in combination with whole wheat flour, oats, and crushed walnuts. The inherent ferulic acid in grains can form an active superposition with coffee polyphenols, making the antioxidant performance of the finished product more stable and long-lasting.
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